1. Field of the Invention
The embodiments of the invention generally relate to a slit valve door for sealing substrate passages in vacuum processing systems.
2. Background of the Related Art
Thin film transistors (TFT) are commonly used for active matrix displays such as computer and television monitors, cell phone displays, personal digital assistants (PDAs), and an increasing number of other devices. Generally, flat panels comprise two glass plates having a layer of liquid crystal materials sandwiched therebetween. At least one of the glass plates includes one conductive film disposed thereon that is coupled to a power source. Power, supplied to the conductive film from the power source, changes the orientation of the crystal material, creating a pattern display.
With the marketplace's acceptance of flat panel technology, the demand for larger displays, increased production and lower manufacturing costs have driven equipment manufacturers to develop new systems that accommodate larger size glass substrates for flat panel display fabricators. Current glass processing equipment is generally configured to accommodate substrates up to about one square meter. Processing equipment configured to accommodate substrate sizes up to and exceeding 4 square meters is envisioned in the immediate future.
Glass substrate processing is typically performed in a cluster tool by subjecting a substrate to a plurality of sequential processes to create devices, conductors, and insulators on the substrate. Each of these processes is generally performed in a process chamber configured to perform a single step of the production process. In order to efficiently complete the entire sequence of processing steps, the cluster tool includes a number of process chambers coupled to a central transfer chamber. A robot is housed in the transfer chamber to facilitate transfer of the substrate between the process chambers and a load lock chamber. The load lock chamber allows substrates to be transferred between the vacuum environment of the cluster tool and an ambient environment of a factory interface. Such cluster tools for glass substrate processing are available from AKT, Inc., a wholly-owned subsidiary of Applied Materials, Inc., of Santa Clara, Calif.
As the substrate size for manufacturing flat panel display grows, the manufacturing equipment for these substrates becomes larger in size as well. Accordingly, the door or gate that isolates one vacuum chamber (or load lock) from another has became larger, or, specifically longer since the slot opening between the two chambers has to become wider to accommodate the large width of the substrate passing through the slot opening. The increasing length of the door poses a technical challenge for obtaining a good isolation seal between the two chambers, which is maintained by an elastomer seal disposed around the slot opening between the door and a chamber wall.
FIG. 1 depicts a partial sectional view of a substrate passage 108 formed through a load lock chamber body 106 and selectively sealed by a conventional slit valve door 110. A seal 116 is deposed between the door 110 and chamber body 106 to provide a vacuum seal across passage 108. The force required to load the seal 116 in order to obtain good chamber isolation is high.
When a vacuum condition is present within the chamber body 106, the pressure differentials cause the chamber body 106 to distort and move relative to the slit valve door 110. As the seal 116 is typically retained in the slit valve door 110, the movement of the chamber body 106 creates a shearing force on the seal, especially in the center of the door span. Moreover, as the seal 116 is urged in one direction by the chamber body 106, the seal 116 is force against the corners of a seal gland 114 formed in the slit valve door 110. Chafing of the seal 116 against the chamber body 106 and the corner of the seal gland 114 creates unwanted particles that may adversely effect substrate processing. Additionally, the seal 116 may become abraded or damaged by the mechanical interaction with the chamber body 106 and the corner of the seal gland 114, thereby significantly shortening the service life of the seal 116.
Therefore, there is a need for an improved slit valve door seal.